Closures for apertures such as vehicle windows, sunroofs and sliding doors are now commonly motor driven. As a further convenience to an operator or passenger of a vehicle, such power windows are frequently provided with control features for the automatic closing and opening of an aperture following a simple, short command from the operator or passenger. For instance, a driver's side window may be commanded to rise from any lowered position to a completely closed position simply by momentarily elevating a portion of a window control switch, then releasing the switch. This is sometimes referred to as an "express close" feature. This feature is commonly provided in conjunction with vehicle sunroofs. Auto manufacturers may also provide these features in conjunction with power doors, hatches or the like. Such automated aperture closing features may also be utilized in various other home or industrial settings.
Other convenience features now being offered for use on vehicles include environmental venting modes, in which vehicle windows are automatically lowered or opened a prescribed distance once a control system determines a certain temperature threshold, internal or external, has been met or exceeded. In addition, a precipitation detection system may be provided for sensing the advent of precipitation and for automatically closing a sunroof, windows or an automatic door. These specific examples pertain to vehicles, though other instances of automatic aperture adjustment are known to one skilled in the art.
In addition to providing added convenience, however, such features introduce a previously unencountered safety hazard. Body parts or inanimate objects may be present within an aperture when a command is given to automatically close the aperture. For example, an automatic window closing feature may be activated due to rain while a pet in the vehicle has its head outside a window. A further example includes a child who has placed its head through a window or sunroof and then itself accidentally initiates an express close operation.
In order to avoid tragic and damaging accidents involving obstacles entrapped by a power window, some vehicles are now provided with systems which detect a condition where a window has been commanded to express close, but which has not after a given period of time. As an example, a system may monitor the time it takes for a window to reach a closed state. If a temporal threshold is exceeded, the window is automatically lowered. Another system monitors the current drain attributed to the motor driving the window. If it exceeds a threshold at an inappropriate time during the closing operation, the window is again lowered.
The problem with such safety systems is that an obstacle must first be entrapped and subject to the closing force of the window or other closure for a discrete period of time before the safety mechanism lowers the window. Limbs may be bruised and fragile objects may be broken by such systems. In addition, if a mechanical failure in the window driving system occurs or if a fuse is blown, the obstacle may remain entrapped.
To address these shortcomings, a system has been proposed which monitors the environment adjacent to or within an aperture, and which may be used as an obstacle detection system, among other applications. This system may be used in conjunction with a power window to prevent activation of an express close mode, to stop such a mode once in progress, or to exit an express close mode and automatically reverse the window motion. The system comprises an emitter positioned in proximity to the aperture to emit a field of radiation adjacent the aperture. A detector is also provided which normally receives radiation reflected from one or more surfaces proximate the aperture. When an obstacle enters the radiation field, it alters the amount of reflected radiation received at the detector. This alteration, if sufficient to meet or exceed a threshold value, can be used to prevent, stop or reverse an express close mode, to activate a warning annunciator, or to initiate some other action.
The economics of producing such a system dictate that it is not feasible to produce a system custom-tailored for the environment of every vehicle in which it is installed. This is also true if the system is installed for some other non-vehicle application. Therefore, depending upon the reflecting characteristics of the environment proximate the aperture, the system detector will provide varying degrees of sensitivity. In one embodiment where the detector registers a high degree of reflectivity from the environment and is triggered by an obstacle which decreases the reflected radiation, it is desirable that the environmental reflectance be maximized. In contrast, in an embodiment where the detector senses a minimum of reflected radiation normally and is triggered by a higher degree of reflectance from an obstacle, it is desired to minimize environmentally reflected radiation. In vehicle applications, radiation reflectance is likely to vary between vehicle manufacturers, between vehicle models and model years, and between individual vehicles, due to the physical orientation of surfaces adjacent an aperture and the materials comprising such surfaces.
Another issue to be addressed with known monitoring systems includes the need to calibrate the various system components, including the reaction of the components to temperature variations. For instance, if the emitter of the monitoring system is comprised of one or more light emitting diodes (LEDs), and the detector is comprised of a photo IC which provides an output pulse which increases in length with increased detected radiation, it is necessary to know in advance what level of receiver gain is necessary to achieve a desired output pulse length for a given LED output.
Further, both the LEDs and a receiver photo IC have a non-trivial response to temperature fluctuations. LED output tends to decrease significantly with increasing temperature, and photo IC responsiveness tends to increase with temperature. Without adequate compensation, these factors render the monitoring system useless in typical vehicle applications.
Additionally, reflecting surfaces adjacent the aperture tend to alter over time. For vehicles, such alteration may be across manufacturers, models, model years and individual vehicles. Thus, a monitoring system initially optimized for a particular environment may not be optimized for the useful life of the system. In the worst case, environmental changes are sufficient to cause reflected energy to register in the system as an obstacle when no obstacle is present.